(1) Field of the Invention
The present invention generally relates to deployment of floatable devices from submerged vessels or vehicles without requiring the vehicle to surface and, more particularly, to flotation of devices towed from a submerged vehicle.
(2) Description of the Prior Art
Submersible vehicles are known and used, with a wide variety of adaptations, for many diverse purposes. In such fields as undersea rescue, exploration and salvage, it is known to deploy manned or unmanned submersible devices from a manned submerged vessel or vehicle. The submersible device, if unmanned, may be towed by cable or controlled remotely though communication links provided in a cable which connects the submersible device to the manned vessel.
Towed vehicles or payloads often may be much more readily surfaced than the manned or programmed-course unmanned vehicle for purposes which can be carried out only at the water surface. The deployment of a radio antenna for communication is a common example of such a purpose, particularly in the case of a programmed-course unmanned vehicle which must periodically obtain position data from a navigational system communicating by radio such as a global positioning system (GPS).
One known method for surfacing a payload is to tow a positively buoyant vehicle on a long cable. Positive buoyancy causes the payload to rise until that positive buoyancy is balanced by downward forces from the cable which will trail the towing vehicle in a curved form due to hydrodynamic drag on the cable itself. Then, as the towing vehicle slows, the cable will become more vertically oriented until the towed payload or vehicle reaches the water surface. However, the drag on the towing cable may be substantial and a significant fraction of the hydrodynamic drag on the towing vehicle, limiting potential speed thereof until the towed payload can carry out its function and be recovered to the submerged vessel. Further, the positive buoyancy can have a significant adverse and somewhat unpredictable effect on the trim of the towing vessel since the towing cable will exert a force on the towing vehicle which will seldom pass through the center of pressure thereof. If the buoyant payload is towed from the stern of the towing vessel, control of depth may become very difficult and compromise the success of surfacing the buoyant payload.
The above described technique can also be modified by use of a specialized run profile as disclosed in U.S. Pat. No. 5,379,034. While useful and advantageous for some specialized purposes, such as the possible application, disclosed therein, to deployment of a Global Positioning System antenna buoy from an unmanned towing vehicle whereby the need for a large, variable buoyancy system sufficient to rapidly surface the towing vehicle is avoided, this modification has the added disadvantage of requiring highly accurate knowledge of towing vehicle velocity, buoyancy and depth as well as limiting the time the payload can be kept on the surface.
It has also been proposed to tow the buoyant payload or deploy it directly from an extendable mast or to use the mast directly for the surface mission, such as radio communication. However, such an extendable mast would require a significant portion of the payload of the towing vehicle and does not avoid but, rather, aggravates the problems associated with hydrodynamic drag and may adversely affect static stability as well as dynamic trim of the towing vessel.
The separation of liquid water into its gaseous components of hydrogen and oxygen by electrolysis is, of course, well-known and a classic demonstration experiment in science classes. Pure water is a very poor conductor of electricity; but when a small amount of an electrolyte, such as an acid, base, or salt, is dissolved in water, the resulting solution readily conducts an electric current. As is generally known, when a current of electricity is passed through a solution of an electrolyte, the ions of the electrolyte are the agencies that carry the current; the ions migrate toward the two electrodes, the positive ions (cations) moving toward the negative electrode (cathode) and the negative ions (anions) moving toward the positive electrode (anode). This process is called electrolysis. When an electric current is passed through water containing a small amount of an electrolyte, such as H.sub.2 SO.sub.4, NaOH, Na.sub.2 SO.sub.4, NaCl, and so forth, bubbles of hydrogen are formed at the cathode and oxygen is evolved at the anode. The volume of hydrogen produced is twice that of the oxygen. The net reaction can be summarized by the equation EQU 2H.sub.2 O+electricity.fwdarw.2H.sub.2 .fwdarw.+O.sub.2 .fwdarw.
It must be borne in mind that the equation only shows what products are formed; it does not suggest a mechanism, which is more complex than suggested by this simple equation alone. For example, if NaCl is used in dilute, non-concentrated levels as an electrolyte in an aqueous solution subjected to electrolysis, it is known that both chlorine gas and oxygen can be generated at the anode while the hydrogen is being formed at the cathode. It is also known that if the aqueous sodium chloride solution is made very dilute, then little chlorine is formed at the anode in addition to the oxygen formed during electrolysis. Suffice it to say that it is an understood principle of basic chemistry, that depending upon the concentration and type of salt constituents present in an aqueous solution, formation of another type of gas, viz. chlorine, is possible in addition to the oxygen and hydrogen formed during electrolysis of water.
In any event, despite the possibility of explosion if, for example, the two gases of oxygen and hydrogen are allowed to mix and then ignited, some practical applications of such a process have been at least proposed. For example, in U.S. Pat. No. 5,167,786 to William J. Eberle, an arrangement for collection of wave-power is proposed. In that system, a toroidal float encircling a central tower moves up and down under the influence of tides and waves, driving a DC generator. Power from the generator is used to separate oxygen and hydrogen by electrolysis and the resulting gases are then pressurized and stored in the toroidal float in order to store the generated gases until they are retrieved. However, since the gas is pressurized and stored in the toroidal float, the buoyancy of the toroidal float is reduced by the added mass of separated gases although, presumably, the gases would be collected before positive buoyancy of the toroidal float was lost or significantly compromised.